Method and device for the fabrication of nuclear fuel compacts

Abstract

In a method for the fabrication of nuclear fuel compacts, a cylindrical mold is filled with coated particles containing fissile and fertile material as well as grains of graphite if necessary. The mold is heated to a temperature above the softening temperature of pitch which is injected into the mold in the hot state through openings provided at regular intervals along the mold wall and having a diameter which is smaller than the size of the coated particles, the injection of pitch being carried out at right angles to the generator-lines of the cylinder formed by the mold.

What we claim is: 
     
       1. A method of fabrication of nuclear fuel compacts in which a cylindrical mold is filled with coated particles containing fissile and fertile materials as well as grains of graphite if necessary and said mold is heated to a temperature which is higher than the softening temperature of pitch, wherein said pitch is injected into said hot mold through openings located at regular intervals over the entire length of a cylindrical wall of the mold, the injection of pitch being performed at right angles to the generator-lines of the cylinder constituted by the mold and through said openings whose diameter is smaller than the size of the coated particles. 
     
     
       2. A method according to claim 1, wherein the pitch is injected in a radial direction pointing towards the exterior of the cylinder, the pitch being stored within an internal cylindrical duct pierced by openings and constituting the internal wall of the mold, thereby producing a compact of annular shape after removal from the mold. 
     
     
       3. A method according to claim 1, wherein the pitch is injected through openings in an outer cylindrical wall of the mold so arranged as to direct the stream of pitch towards the axis of the cylinder, said openings being fed by channels in said outer cylindrical wall connecting with an external supply of melted pitch supplied under pressure, thereby to form a solid cylindrical compact. 
     
     
       4. A device for the fabrication of nuclear fuel compacts, wherein said device comprises: a mold of approximately annular shape filled with coated particles and if necessary with grains of graphite,   means for controlling the temperature of said mold,   a hollow cylindrical central duct forming the internal wall of said mold and containing pitch under pressure, said duct being pierced by radial openings through which the pitch is injected into the mold,   two pistons performing the function of plugs, said pistons being located at the upper and lower ends of said mold, one of them supporting said central duct, and   means, including a channel through said piston supporting said duct, for injecting the pitch under pressure into the central duct.   
     
     
       5. A device according to claim 4, wherein the central duct contains a leak-tight piping system in which a thermal fluid is circulated. 
     
     
       6. A device for the fabrication of nuclear fuel compacts, wherein said device comprises: a mold of approximately cylindrical shape filled with coated particles and if necessary with grains of graphite,   means for controlling the temperature of said mold,   channels cut in the mold wall and radial openings connecting said channels with the interior of the mold, said openings being of a cross-section smaller than those of said particles and grains,   two plungers which perform the function of end plugs and are located at the upper and lower ends of said mold,   means for injecting pitch under pressure into the interior of said channels.   
     
     
       7. A device according to claim 5, wherein said device comprises a system for the circulation of a temperature-controlled thermal fluid which is in contact with the mold wall. 
     
     
       8. A method according to claim 1, wherein the temperature of injection of the pitch is in the vicinity of 180° C and the injection pressure of said pitch is in the vicinity of 80 bar.